Peter Larsen

Population-Based Epidemiology of Tibial Plateau Fractures

Although epidemiologic studies of tibial plateau fractures have been conducted, none have included geographically defined populations or a validated fracture classification based on computed tomography (CT). The goals of this study were to provide up-to-date information on the incidence and basic epidemiology of tibial plateau fractures in a large unselected patient population and to report the mechanisms of injury involved and the distribution of fractures according to a validated CT-based fracture classification. The authors conducted a population-based epidemiologic study of all patients treated for tibial plateau fracture over a 6-year period from 2005 to 2010. The study was based on an average background population of 576,364 citizens. A retrospective review of hospital records was performed. During this time, a total of 355 patients were treated for tibial plateau fracture. This group included 166 men and 189 women, and mean age was 52.6 years (SD, 18.3). The most common fracture type was AO type 41-B3, representing 35% of all tibial plateau fractures. The second most common fracture type was AO type 41-C3, representing 17% of all tibial plateau fractures. The incidence of tibial plateau fractures was 10.3 per 100,000 annually. Compared with women, men younger than 50 years had a higher incidence of fractures. The incidence of fractures increased markedly in women older than 50 years but decreased in men older than 50 years. In both sexes, the highest frequency was between the ages of 40 and 60 years.

Incidence and epidemiology of tibial shaft fractures

INTRODUCTION The literature lacks recent population-based epidemiology studies of the incidence, trauma mechanism and fracture classification of tibial shaft fractures. The purpose of this study was to provide up-to-date information on the incidence of tibial shaft fractures in a large and complete population and report the distribution of fracture classification, trauma mechanism and patient baseline demographics. METHODS Retrospective reviews of clinical and radiological records. RESULTS A total of 196 patients were treated for 198 tibial shaft fractures in the years 2009 and 2010. The mean age at time of fracture was 38.5 (21.2SD) years. The incidence of tibial shaft fracture was 16.9/100,000/year. Males have the highest incidence of 21.5/100,000/year and present with the highest frequency between the age of 10 and 20, whereas women have a frequency of 12.3/100,000/year and have the highest frequency between the age of 30 and 40. AO-type 42-A1 was the most common fracture type, representing 34% of all tibial shaft fractures. The majority of tibial shaft fractures occur during walking, indoor activity and sports. The distribution among genders shows that males present a higher frequency of fractures while participating in sports activities and walking. Women present the highest frequency of fractures while walking and during indoor activities. CONCLUSION This study shows an incidence of 16.9/100,000/year for tibial shaft fractures. AO-type 42-A1 was the most common fracture type, representing 34% of all tibial shaft fractures.

Restrictions in quality of life after intramedullary nailing of tibial shaft fracture: a retrospective follow-up study of 223 cases.

Objective: To evaluate the long-term outcome after intramedullary nailing of tibial shaft fracture. Design: Retrospective, cross-sectional study. Setting: Level I, Trauma Center. Methods: Retrospective review of 294 patients treated with intramedullary nailing after tibial shaft fracture from 1998 to 2008. The participants completed Knee injury and Osteoarthritis Outcome Score, and these data were compared with published reference population. Intervention: Intramedullary nailing of tibial shaft fracture. Main Outcome Measures: Knee Injury and Osteoarthritis Outcome Score. Results: A total of 223 patients agreed to participate (76%). Mean time of follow-up was 7.9 years. Compared to reference population, the study group reported 44% higher incidence of knee pain, 39% higher incidence of function in daily living limitations, 58% higher incidence of limitations in quality of life, and 60% higher incidence of limitations during sports activities. Comparison of age-related differences between the study group and reference population showed that the age group of 18–34 years reported the most difficulties. Conclusions: Compared with reference population, 60% of the patients experienced limitations in activity and restrictions in quality of life and 44% reported knee pain. This was mainly evident among the young participants. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Inbreeding affects fecundity of American mink (Neovison vison) in Danish farm mink.

Inbreeding is an increasing problem in farmed mink, because of limited exchange of individuals between farms. In this study, genetic relatedness within seven American mink (Neovison vison) colour strains originating from 13 different mink farms in Denmark was analysed using 21 polymorphic microsatellite loci. We detected large differences in the level of relatedness (range 0.017-0.520) within colour strains. Moreover, a very strong and highly significant negative correlation between the level of relatedness and fecundity was observed (r = 0.536, P < 0.001) [Correction added after online publication on 9 March 2011: r(2) has been changed to r]. To our knowledge, this is the first time that such a correlation has been demonstrated for commercially farmed mink.

Incidence and Epidemiology of Patellar Fractures.

The literature lacks large-scale, up-to-date, population-based epidemiology studies on the incidence of patellar fractures based on complete populations. The purpose of this study was to provide up-to-date information concerning the incidence of patellar fractures in a large and complete population spanning a decade and to report on the distribution of fracture classification, trauma mechanisms, and patient baseline demographics. A retrospective review of clinical and radiological records of 756 patellar fractures treated between 2005 and 2014 was conducted. Mean age at the time of fracture was 54±21 years. Mean age was 46±22 years for males and 61±18 years for females. The sex distribution was 425 (56%) females and 331 (44%) males. The incidence of patellar fractures between 2005 and 2014 was 13.1/100,000/ year with a year-to-year variation between 10.5 and 16.5/100,000/year during the 10-year observation period. The distribution of incidence shows an increase with increasing age. Males have the highest incidence of fracture in the 10-to-19-year age group, approximately 15.4/100,000/year. Females in the 60-to-80-year age group have the highest incidence, approximately 36/100,000/year. AO type 34-C3 was the most common fracture type, representing 25% of all patellar fractures, followed by AO type 34-C1, representing 23%. [Orthopedics. 2016; 39(6):e1154-e1158.].

Population-based epidemiology of 9767 ankle fractures

BACKGROUND The purpose was to provide up-to-date information concerning the incidence of ankle fractures in a large and complete population including all age groups, spanning a decade, and report the distribution of fractures, trauma mechanism and patient baseline demographics. METHODS Population-based epidemiological study of all patients treated for an ankle fracture in a 10-year period from 2005 to 2014. RESULTS A total of 9767 patients with ankle fractures were treated between 2005 and 2014. The mean age at time of fracture was 41.4 (24.3 SD) years. The mean incidence of ankle fractures between 2005 and 2014 was 168.7/100,000/year. Years with cold winters showed increased incidences compared with years with normal winters. For males, the incidence was 157.1/100,000/year, and for females, 179.5/100,000/year. The incidence shows a peak incidence among adolescents in both genders with a male predominance. After the age of 19 the male incidence declines with age, which is in contrast to females, who experience an increasing incidence. The most common fracture type in all age groups was a fracture of the lateral malleolus representing 55% of all fractures. The predominant mode of injury was falls (61%) followed by sports (22%). CONCLUSION This study shows an incidence of 168.7/100,000/year spanning a decade. The most common fracture type in all age groups was a fracture of the lateral malleolus representing 55% of all fractures. The predominant mode of injury was falls (61%) followed by sports (22%).

Heterosis and genetic variation in the litter size of purebred and crossbred mink

Crosses between different mink lines from 3 Danish mink farms that use different breeding strategies were studied to estimate heterosis and variance components for litter size. The study was designed to analyze crosses between lines of the same color type, between different color types, and between animals originating from different farms. Effect of heterosis, color type, and variance components were estimated using Average information REML (AI-REML) algorithm implemented in the DMU package for analyzing multivariate mixed models. Females from 7 generations that gave birth to at least 1 offspring were analyzed and the effects of parity and production year were included in the analyses. Genetic trend and the proportions of the total variance explained by the effects of additive genetics (h2), common environment (due to repeated litters from the same female; c2), and dam of the female (granddame of the born litter; d2) were estimated. The results showed that mink of the Black color type potentially produced smaller litters compared to mink of the other studied color types. We found significant general maternal effect of heterosis for litter size. Analyses of specific heterosis showed a significant positive effect of crossing between lines of the same color type. Estimates of variance components revealed h2 levels for farm A, B, and C of 0.15, 0.06, and 0.09, respectively; thus litter size could be selected for in the future. The effect of common environment on litter size was also considerable, with c2 values of 0.005, 0.11, and 0.15 at farms A, B, and C, respectively. In conclusion, we recommend genetic selection as a means of increasing litter size in farmed mink.

Local and Widespread Hyperalgesia After Isolated Tibial Shaft Fractures Treated with Intramedullary Nailing

OBJECTIVES Knee pain is accepted as a common complication to intramedullary nailing of tibial fractures. However, no studies have systematically studied the pain sequel following tibial fractures. The objective of this study was to assess pain and hyperalgesia from 6 weeks to 12 months postoperatively after intramedullary nailing of tibial shaft fracture. METHODS A total of 39 patients were included in this 12-month follow-up study. After 6 weeks, 3, 6, and 12 months postoperatively the pain intensity was measured on a visual analog scale (VAS) and the pressure pain sensitivity was assessed bilaterally by pain pressure thresholds (PPTs). RESULTS The mean age at the time of fracture was 42.9 years. Twelve months after surgery, the pain intensity for worst pain during the last 24 hours was 1.8 ± 2.7 cm. The PPTs progressively increased from 6 weeks after surgery to 12 months postoperatively for all PPT sites except for the forearm (P < 0.012). Moreover, the PPTs on the leg were generally reduced on the injured side compared with the non-injured side (P < 0.04). CONCLUSIONS This study suggests that localized, distal, and bilateral hyperalgesia are common following an isolated tibial shaft fracture treated with intramedullary nailing, although no widespread (extrasegmental) hyperalgesia was detected. Such observations may be important for developing the most adequate rehabilitation procedure following a tibial fracture.

Population genetic structure in farm and feral American mink (Neovison vison) inferred from RAD sequencing-generated single nucleotide polymorphisms

Feral American mink populations (), derived from mink farms, are widespread in Europe. In this study we investigated genetic diversity and genetic differentiation between feral and farm mink using a panel of genetic markers (194 SNP) generated from RAD sequencing data. Sampling included a total of 211 individuals from 14 populations, 4 feral and 10 from farms, the latter including a total of 7 color types (Brown, Black, Mahogany, Sapphire, White, Pearl, and Silver). Our study revealed similar low levels of genetic diversity in both farm and feral mink. Results are consistent with small effective population size as a consequence of line selection in the farms and founder effects of a few escapees from the farms in feral populations. Moderately high genetic differentiation was found between farm and feral animals, suggesting a scenario in which wild populations were founded from farm escapes a few decades ago. Currently, escapes and gene flow are probably limited. Genetic differentiation was higher among farm color types than among farms, consistent with line selection using few individuals to create the lines. Finally, no indications of inbreeding were found in either farm or feral samples, with significant negative values found in most farm samples, showing farms are successful in avoiding inbreeding.

A novel tool for measuring ankle dorsiflexion: A study of its reliability in patients following ankle fractures

BACKGROUND Assessment of ankle joint movement in a weight bearing position has important clinical implications. The lunge ankle dorsiflexion measurement device (LAD) has been developed with the aim of facilitating ease of and standardisation of the measurement of ankle joint movement. The literature lacks studies evaluating the reliability of weight bearing measurements of the ankle joint in study groups with ankle disabilities. The objective of this study was to examine the intra- and inter-tester reliability of ankle dorsiflexion measured with the novel LAD in patients following a fracture of the ankle. METHOD This study was a randomized intra- and inter-tester reliability study with blinding of testers and participants. All participants were tested twice by each tester, with the order of testers randomized. The intra- and inter-tester reliability was assessed by the calculation of interclass correlation coefficients (ICC). RESULTS The study sample consisted of 24 patients: 15 females and nine males post-immobilisation following surgery for ankle fractures. The mean age was 51.0 years, ranging from 22 to 92 years. All patients had sustained an AO classification 44- fracture of the ankle. The mean follow-up time was 9.3 months (16.2 SD) after the time of fracture. The inter-tester reliability was high, with an ICC of 0.984 (95%CI: 0.963-0.993) and SEmeas of 0.14cm. The ICC for Tester A was 0.989 (95%CI: 0.974-0.995) and SEmeas 0.10cm. The ICC for Tester B was 0.990 (95%CI: 0.977-0.996) and SEmeas 0.09cm. CONCLUSION This study shows a high inter- and intra-tester reliability for measuring ankle dorsiflexion with the LAD following a fracture of the ankle.